Unlike the Sharp EL-520W<\/a> or the Casio fx-260Solar<\/a>, the TI-30XA does not require you to be in a certain mode to use the statistical functions. Similar to the Casio, however, the TI-30XA is reverse entry. Therefore, to enter -18, you key in 18, then<\/em> + \u2194 –<\/span>.<\/p>\n Example: Find the standard devation of the data set {-18,16,0,45,100,32,27}.<\/strong><\/p>\n Solution:<\/strong> First, you should clear any data already in there. To do so, press 2nd<\/span> 7<\/span>. (If the stats memory is already clear, you’ll get Error<\/em>. Don’t worry; just press ON<\/sup>⁄C<\/sub><\/span>.) Notice the yellow CSR above the 7; I believe it stands for “Clear Stats Registers”.<\/p>\n Enter each number, pressing the \u03a3+<\/span> button after each. After you enter -18, then press \u03a3+<\/span>, you should see “n=1” across the screen. Then, key in 16 and press \u03a3+<\/span>, and so on. If you make a mistake, you can pressON<\/sup>⁄C<\/sub><\/span>, then enter the correct number and continue by pressing \u03a3+<\/span>. If you want to remove an entry from the list later on, you can do so with 2nd<\/span> \u03a3+<\/span>. Noticing the yellow \u03a3- printed above the \u03a3+<\/span>, you’ll get the idea.<\/p>\n Once you’ve entered the last number (in our case, 27), then pressed \u03a3+<\/span>, it’s time to find the standard deviation. If you want\u00a0\u03c3n<\/sub>, press 2nd<\/span> \u00f7<\/span> (once again, see the yellow \u03c3xn<\/sub> above \u00f7<\/span>). You should get 34.9, just like in the previous two articles. Otherwise, press 2nd<\/span> \u221ax<\/span> to get \u03c3n-1<\/sub>. For Math Foundations 11, I believe \u03c3n<\/sub> is preferred.<\/p>\n Because the calculator I had in high school was similar to the TI-30XA, writing this article has been somewhat of a homecoming for me. I still appreciate the simple layout, with dedicated keys for square root and data entry.<\/p>\n Have a great weekend:)<\/p>\n